drm/tiny/ofdrm: Use fbdev-shmem

Implement fbdev emulation with fbdev-shmem. Avoids the overhead of
fbdev-generic's additional shadow buffering. No functional changes.

Signed-off-by: Thomas Zimmermann <[e-mail]>
Cc: Thomas Zimmermann <[e-mail]>
Cc: Javier Martinez Canillas <[e-mail]>
Reviewed-by: Javier Martinez Canillas <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/tiny/ofdrm.c

···
 #include <drm/drm_damage_helper.h>
 #include <drm/drm_device.h>
 #include <drm/drm_drv.h>
-#include <drm/drm_fbdev_generic.h>
+#include <drm/drm_fbdev_shmem.h>
 #include <drm/drm_format_helper.h>
 #include <drm/drm_framebuffer.h>
 #include <drm/drm_gem_atomic_helper.h>
···
 	if (color_mode == 16)
 		color_mode = odev->format->depth; // can be 15 or 16
 
-	drm_fbdev_generic_setup(dev, color_mode);
+	drm_fbdev_shmem_setup(dev, color_mode);
 
 	return 0;
 }